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steppenwolf

The Rosette Nebula

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The Rosette Nebula - NGC 2237 - Caldwell 49

Ha and OIII Bi-colour image with synthetic green

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Image details: 12 x 600 sec. Ha subframes and 24 x 600 sec. OIII subframes. Ha mapped to red, OIII mapped to blue and a synthesised green channel added.

General Description

The beautiful Rosette Nebula sits at the far western edge of a large molecular cloud in the constellation of Monoceros. Often designated as NGC 2237, this actually refers to just one part of the overall structure. Other important nebulous regions within the Rosette include NGC 2238 and 2246 and there is an open cluster, NGC 2244 right at the core of the nebula. Another open cluster, NGC 2252 can be found on the northeastern limb of the nebula.

The nebula responds well to LRGB (including one shot colour) and narrowband filtering as it is rich in active HII regions. Unusually, it is even worth using a Hydrogen Beta (Hb) filter on this object.

One Shot Colour

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Image details: 13 x 600 sec. OSC subframes for colour, 25 x 600 OSC subframes converted to mono for partial false luminance

I much prefer narrowband imaging for this object and in particular, I like simple mono Ha images

Ha mono

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Image details: 21 x 600 sec. Ha subframes captured during a completely automatic unattended session

Because of limited imaging opportunities in the UK, I also take advantage of bi-colour narrowband imaging where I map Ha to red and OIII to both green and blue

Ha and OIII bi-colour

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Discovery

There is a little confusion over the designation of some regions of this object and I’ll try to unravel the story as best I can but please note that what follows is only my own interpretation of the available data! The open cluster, NGC 2239 was discovered by Sir William Herschel in 1784 then again by John Herschel in 1830, however, the same object was previously discovered by John Flamsteed in 1690 and was later designated NGC 2244. So, NGC 2239 and NGC 2244 are actually the same object!

It wasn’t until 80 years after William Herschels’ discovery of the cluster that the first region of nebulosity was revealed by Albert Marth, a German astronomer who is credited with finding over 600 nebulae. This small region, NGC 2238 described by Marth as ‘a small star with nebulosity’, was most likely all he could discern with his narrow field of view. However, Lewis Swift fared better when he discovered NGC 2237 in 1883 followed 3 years later by NGC 2246.

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What gives the nebula its shape?

The core of the nebula appears as a hollowed out chamber and in fact that is pretty much what it is. The hot young stars in the open cluster NGC 2244, notably HD 46223 and HD 46150 have large ionising luminosities, which are responsible for the HII region. However, they also contribute substantially, along with their fellow cluster members, to the stellar winds that push outwards from the cluster at around 20km/sec. These stellar winds displace the core gases creating the cavity that we can see in the centre of the nebula.

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Star Formation

The Rosette Nebula is a region of intense star formation. The stellar winds from the young stars within the nebula exert a high pressure on the interstellar clouds, compressing them and it is this compression that leads to ongoing star formation.

There are several obscuring dark veins of matter (not to be confused with ‘veins of dark matter’!) within the nebula. Close examination of these veins reveals tiny dark blobs of matter. These dark blobs are known as Bok Globules after the Dutch born Harvard Professor Bartholomeus (Bart) Jan Bok. Bok suggested that the globules were at one time attached to umbilical filaments of neutral Hydrogen gas. Radiation from local stars first separated and then compressed the filaments leaving individual small areas of matter that continued to contract under the pull of their own gravity until they formed the globules visible today. It is believed that these globules contain primeval dust clouds from which new stars are being formed.
 

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How to locate the Rosette Nebula

Start by locating the constellation of Orion. Draw a line between Orion’s head star Lambda (λ) Orionis and the very bright orange star Betelgeuse and extend the line twice the distance again with a slight bend upwards to find the dazzling open cluster NGC 2244 - also known as Caldwell 50 - which lies at the centre of the Rosette Nebula. The cluster is easy to see in a 6-inch telescope but the nebulosity will require a 10-inch or larger instrument to reveal its true beauty, which will be enhanced by the use of a UHC filter.

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Statistics

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What a wonderful capture and presentation.

This gives another purpose to our images and is a great example.

I also like the depth of the images.

Thank you!

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Wow, that's quite a project Steve - nice images and nice write up!!

James

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Lovely images, also, a well written and informative post.

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Great stuff, Steve. I'm a fan of the first one, most, I think. It's very 'gassy' looking, the stars are tiny (which helps the sense of scale) and the inner regions show a gently different colour thanks to the OIII contribution.

Cracking write up as well, with all sorts of history I didn't know. With regard to Bart Bok the only biographical detail I can think to add was that (and I'm really not making this up) he had a private ambition to urinate in all the great rivers of the world before shuffling off his mortal coil. Well, on that note... 

:icon_biggrin: lly

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Marvellous presentation and lots to take in. Thanks for posting. Cakes are on me at Lucksall. And as for the toilet humour from Olly....

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Very nice! There's a subtle 3D quality to the first images which I find most appealing.

Did you post a version of this image last year? At least, I seem to recall an equally impressive capture. Maybe I'm thinking of someone else. I forget, probably my age ;-)

Regards

John

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Thank you Steve for the most excellent, erudite and educational write-up, not to mention the super images and diagrams that you've sprinkled (like stardust) throughout.

You've raised the bar and we'll expect the same from you every time we get a couple of days of clear weather from now onwards. ;)

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Agreed, this is an lovely composition of high quality images/processing together with very informative text - great work.

Martin

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What super images there and some fantastic information to go with it. thanks for sharing

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Fantastic write-up Steve, I've learnt there's a LOT more to the Rosette than meats the eye. You've obviously put a lot of work into making this an informative piece so thanks :)

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The first image is just a cracker. Very light and gaseous and just hangs like well a gas cloud should. Great write up as well, thought i was on Wiki for a minute.

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The first image is just a cracker. Very light and gaseous and just hangs like well a gas cloud should. Great write up as well, thought i was on Wiki for a minute.

Nah...This is based in fact ;)

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Thank you for your kind comments, folks, it has made the effort even more worthwhile for me!

Like many of us, I have been plagued with appalling weather over what should have been the prize portion of the imaging calendar but I wanted to keep my interest going so this little project allowed me to collate the small amount of data that I was able to collect in the last month and do something different with it.

My wife, Janie, cannot believe that there is actually someone else out there who likes a mono image - she doesn't!

With regard to Bart Bok the only biographical detail I can think to add was that (and I'm really not making this up) he had a private ambition to urinate in all the great rivers of the world before shuffling off his mortal coil.

That didn't come up in my research, Olly but thank you for completing the micro biography! I like a man with ambition, I wonder if he was 'aiming' high or low?

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Must have been a 'slow news week' at the mag... That's a fantastic image post, rich in imagery and content. I definitely prefer the bi-colour image, it has a beautiful 3D nature to it. The write up is very interesting and sets a new precedent for all future image posts!

Give the man a gold star...

Olly, your addition made me chuckle.

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